Connections of cult horse I’m Thunderstruck and racing fans alike are mourning the shock death of the baldy-faced son of Shocking.

The two-time Group One winner for Mick Price and Michael Kent Jnr passed away after an incident following a routine knee operation late on Thursday afternoon.

Originally prepared in New Zealand by Daniel Miller, for whom he won a trial at Te Aroha, I’m Thunderstruck was purchased by OTI Racing, and went on to win seven of his 23 starts, with a further 8 placings.

In addition to Group One wins in the Makybe Diva Stakes (1600m) and Toorak Handicap (1600m), he was also narrowly touched off by Anamoe in last year’s Gr.1 Cox Plate (2040m).

With the lucrative Golden Eagle (1500m) also on the mantlepiece, I’m Thunderstruck won in excess of A$8 million and resonated with racing fans care of his catchy name, booming finish and regular stoushes with a good group of weight-for-age adversaries which included Anamoe, Mr Brightside and Alligator Blood.

"It's something that can happen after an operation and unfortunately, it's happened with this horse," OTI's Terry Henderson told Racing.com.

"As you can imagine, the owners, the staff at Mick and Michael's stable are devastated. We just have to face the reality that this is one of those terrible things that can happen when you are trying to look after the horse as best as we can.

"It was a relatively simple procedure which has gone horribly wrong.

"The procedure went perfectly fine. The horse got up to recover from the surgery and initially appeared OK. But then he was very, very lame on the off side knee and clearly something was wrong.

"They took X-rays of it and there were multiple fractures in the knee. So obviously at some stage he has put weight on that knee in a manner which has caused that injury.

"From a humane point of view, we had no choice."

His New Zealand breeders Tony Forlong and Jenny Jones were also coming to grips with the loss of their pride and joy, with AC/DC fan Forlong responsible for naming him.

“We at Epona Park, the breeders of I’m Thunderstruck or Whiteboard as we knew him are devastated by the news overnight,” they said.

“From the first time we met him as a new born foal we knew he was special, ordering his mum around. A tough horse all his life, giving Eion Kemp one of his hardest challenges to break and then go on to be a champion.

“We will never forget him with his race picture hanging with pride in our barn.

“We wish to thank everyone involved in his development particularly Don Mackinnon guiding his development as a young horse to all the Vets, Farriers, breakers trainers that all played a part in shaping Whiteboard to realise his potential with OTI and Mick Price and Michael Kent Jnr.”

By Rich Hill Stud stallion Shocking, I’m Thunderstruck is out of the Edenwold mare Primadonna Girl.

An emotional Michael Kent Jnr said on Thursday night he would honour his promise and give the popular galloper his forever home at his farm.

"Ali and I have been in tears all night. We always said we'd love to have him back at our farm when he is finished," Kent Jnr said.

"We will still keep our promise and if the owners are okay, we will find a nice place to bury him. A nice park there.

"It's tough. He is a very special horse to everyone. Forget he is a good horse, he is just a beautiful horse and so intelligent.

"He has changed everyone's lives. To lose any horse is terrible, but to lose one like that is awful with the way it happened.”